Molded snowshoe with pliable heel contact area

ABSTRACT

A molded plastic snowshoe of the type with a boot binding permitting pivoting in the pitch direction has a boot heel contact area formed of a flexible material. This provides for a soft strike as the boot comes in contact with the snowshoe deck in each step, eliminating the noise that usually accompanies the heel strike on a hard deck, and also increases comfort in use of the snowshoe, with the hard strike feel eliminated. Another advantage is that with a cleat mounted at the bottom of the soft section of decking the snowshoe adapts better to irregularities of terrain since the heel cleat is essentially suspended relative to the stiffer molded portions of the snowshoe. The flexibly suspended heel cleat can be pushed down to engage with snow or ice despite the irregular surface of the terrain and the rigidness of the snowshoe deck surrounding the cleat area.

BACKGROUND OF THE INVENTION

This invention relates to the field of snowshoes, and in particular snowshoes constructed of injection or compression molded materials such as polymers or composites.

A number of snowshoes in the commercial market place are made by injection molding of polymers. These snowshoes typically consist of a molded deck, which provides a surface for flotation on the snow, a surface for attaching traction elements to the bottom, and a structure to which a binding can be attached to hold the shoe or boot of the user. The deck of a snowshoe in this category usually is of injection molded plastic of thickness approximately 3-4 mm. Alternately the deck could consist of a fiber reinforced composite of appropriate thickness. Since snowshoes of this design do not rely on a peripheral structural frame for any of the structure of the snowshoe, the deck itself is typically rather rigid (flexural rigidity) so that the structure can support the flotation loads required by the snowshoe and the concentrated load inputs from the attachment to the user's foot, as well as supporting traction elements normally affixed to the snowshoe structure.

The molded snowshoe provides a surface in the area of the user's heel or rear portion of the foot on which the foot or heel can rest when bearing weight.

Materials from which molded snowshoes are produced are usually polymers, or reinforced polymers with moduli of elasticity of approximately 350,000 or higher.

The molded plastic snowshoes have exhibited some problems, primarily due to the stiffness and hardness of the deck. One issue has been noise; the molded snowshoe presents a relatively hard surface against which the heel of the user strikes upon contact with the terrain surface. This produces a sharp tapping noise with each step. This hard impact with each step also tends to be uncomfortable. Another problem is with traction. The typical molded snowshoe provides an essentially rigid support structure for any traction elements mounted on the underside of the snowshoe. This rigidity does not allow preferential pressure to be applied to the traction elements through direct weighting of the snowshoe at the point of the traction elements, allowing virtually no deformation of the snowshoe structure for adaptation to the terrain by directing force through those traction elements where it is needed. On uneven terrain, traction elements such as a heel cleat mounted on the deck beneath the user's heel may not come into any engaging contact with the snow or ice.

In the prior art, traditional snowshoes formed of wood frames and rawhide lacing for a decking surface provide a structure that has a good inherent level of sound deadening, since there was no heel strike on a hard surface. Similarly, snowshoes having frames formed of aluminum tubing supporting a stretched flexible decking avoid the situation of a sharp heel strike against a rigid surface, but these snowshoes can still exhibit a certain inherent level of noise particularly as the aluminum frame drags, due to the relatively low damping and the mass and modulus of electricity of the aluminum used for the frame. In addition, the decking material selected for an aluminum framed snowshoe further influences the noise generated by the shoe, with some decking materials providing less sound transmission and more sound dampening than others.

The difficult problem arises with conventional molded snowshoes, as outlined above, which are comprised in most of their area by polymeric materials that are hard and relatively rigid during use. These materials will generate a rather high level of noise when impacted by the boot heel and have limited sound damping characteristics, as well as having the comfort and traction stiffness problems outlined above.

The present invention addresses these problems as described below.

SUMMARY OF THE INVENTION

In the current invention a molded plastic or composite snowshoe has an open area at the vicinity of the heel strike, with a soft, pliable heel strike insert across this area. This material preferably supports a heel cleat at the bottom side, directly below the position of heel strike. The material in the soft region is one that is at or above its glass transition temperature during use, such as an elastomer. This dampens the sound and reduces sound transmission as compared to a conventional molded snowshoe.

The impact forces of the user's boot striking the deck of the snowshoe is determined by the materials and construction of the snowshoe. As noted above, traditional wood frame snowshoes with rawhide lacing provide a platform for the heel to strike with some degree of compliance due to this construction. This compliance reduces the impact forces compared to a rigid surfaces. Similarly, aluminum frame snowshoes with stretched, suspended plastic film or plastic coated fabric also provide a surface with some compliance, reducing the magnitude of impact loads that result when the user's boot contacts the snowshoe.

However, the category of snowshoes formed of molded plastic or composite materials is very different. The molded plastic structure is far more rigid, particularly in the region under the foot, than either of the previous constructions described. The typical construction of molded snowshoes employs materials having moduli of elasticity of around 350,000 psi or greater, in thicknesses of usually about 3 to 4 mm, resulting in a relatively rigid structure, and in particular, rigid against yielding distortion in the vertical direction in the region where the user's boot contacts the upper surface of the snowshoe. The invention solves this problem by providing a soft and flexible material, which may be an elastomeric material, across the open heel area in the region of contact from the heel of the user's boot. In this way the invention achieves the goal of combining the advantages of the molded plastic snowshoe with aspects of noise reduction, comfort and terrain conforming ability which are inherent in the previous types of construction outlined above.

In further explanation, traction for snowshoes on snow and ice surfaces is typically achieved by placing elements having shapes (e.g. a sharp blade like shape with teeth) suited for digging into the snow or ice surface on the lower side of the snowshoe in areas that contact the snow or ice. These elements can be mounted in various locations and can consist of various materials and shapes. The snowshoe's binding typically has a cleat or traction element, mounted under the ball or toe area of the foot. To generate traction, it is necessary to apply pressure to these elements so they can penetrate the surface of the snow or ice. It is known that traction elements can be arranged in portions of the snowshoe that are part of a rigid structure, or they can be located on a relatively flexible support structure such as on the underside of a coated fabric deck on certain constructions of snowshoes (as in U.S. Pat. No. 6,006,453, for example), or on the underside of a binding that is suspended from the snowshoe with various binding suspension systems that are currently employed in the field. An advantage of locating traction on a portion of the structure that is non-rigid with respect to the overall snowshoe structure is that the traction element can have pressure selectively applied to it by direct pressure on top of the snowshoe in the general location where this traction is located. However, the construction of molded snowshoes is such that the structure of the shoe is characterized by one relatively rigid plate or grid structure which precludes the mounting of traction in an area having flexibility. Thus the advantage described above of achieving enhanced traction by the application of pressure generally above the traction element cannot be achieved. The present invention overcomes this limitation by the inclusion of the soft region to which traction elements can be mounted, thus achieving the advantages of traction elements with preferential pressure application.

It is thus among the objects of the invention to combine the advantages of the plastic molded snowshoe with a soft strike feature which reduces noise, increases comfort and increases engagement with the terrain by traction elements. These and other objects, advantages and features of the invention will be apparent from the following description of a preferred embodiment, considered along with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view showing a molded snowshoe body showing a feature of the invention.

FIG. 2 is a perspective view showing the complete snowshoe, with boot binding.

FIG. 3 is another perspective view showing the snowshoe.

FIG. 4 is a perspective view showing a part of the bottom side of the snowshoe and illustrating features of the invention.

FIG. 5 is a top plan view showing a snowshoe body with a different embodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 is a top view showing a snowshoe body 10 according to the invention, without binding. The snowshoe body is molded of a relatively rigid plastic material, which may be a reinforced composite, examples being polypropylene and nylon. Preferred thickness through most of the snowshoe body is about 3.3 mm, or a range of about 3-4 mm. As seen in the drawing, the molded snowshoe body includes a nose portion 12, a central portion 14 and a tail 16. The snowshoe body is molded with a large open area at 18 and continuing back to the region 20 in the drawing. Although this is shown as one large open area, it could instead be embodied as a forward open area generally at 18 and a rear, heel strike region open area generally at 20. The forward open area is provided for a boot binding which is permitted pitch pivoting movement, as described below with reference to FIGS. 2 and 3. The heel area opening, generally at 20, is provided for the soft strike heel feature described above.

In the particular embodiment shown in FIGS. 1-4, the soft strike feature is provided by a soft heel strike insert 22 secured to and suspended on the molded snowshoe body 10 such as by rivets 24 positioned around the periphery of the insert 22 and securing the insert to the snowshoe body by outwardly extending connecting legs 26, 28 and 30 as shown in FIG. 1. This soft strike insert may be, for example, approximately 15 cm long at minimum dimension to about 20 cm long at maximum dimension (about 6″ to 8″), and about 11 cm wide at minimum to about 14 cm wide at maximum (about 4¼″ to about 5½″), as one example. In a preferred embodiment these dimensions can vary by about 3 cm in either direction. This insert 22 probably is non-planar, with an upwardly relieved area 31 on which the boot will rest.

The soft strike insert 22 in one preferred form is injection molded of polyurethane, an elastomeric polymer, and is at or above its glass transition temperature in the environment of anticipated use (as contrasted to the molded body, which operates below its glass transition temperature). Alternative materials are natural rubber, styrene block copolymer elastomer, neoprene, and fabric coated neoprene, as well as other suitable elastomers. The insert may have a thickness range of about 2-4 mm depending on shape. The insert preferably is of durometer about 85 A, or a range of about 70 A to 85 A. This provides for elasticity, with the proper amount of softness and “give” when engaged by the user's shoe or boot (boot is used to mean either shoe or boot herein), and provides good sound damping. The insert 22 is located in the snowshoe generally where the heel and rear half to two-thirds of the user's boot will contact and rest on the upper surface of the snowshoe.

In a preferred embodiment the soft heel insert will deflect down relative to the snowshoe body at least about one-half inch when used by a person of about 160 pounds or more.

FIG. 2 shows the complete snowshoe 35, with a boot binding 36 secured in a pivoted connection to the molded snowshoe body 10. The binding 36 includes a toe cleat (not shown) and the pivot connection can be supported via a traction rail discussed below with reference to FIG. 4, or otherwise supported by the plastic molded body 10. The binding can be configured as in other known snowshoe bindings, and may be similar to other Tubbs Snowshoe binding. The binding includes a heel strap 38, which wraps about the heel of the user's boot when the boot is secured in the snowshoe binding. Although FIG. 2 shows the binding pivoted upwardly (or the snowshoe downwardly, as when a step is taken by the user), FIG. 3 shows the binding down against the snowshoe deck and indicates the general position of the boot, particularly the heel and rear portion of the boot, in the binding and relative to the soft strike insert 22. Ridges 40 are shown on the top surface of the soft strike insert in a primary region for engagement by the boot heel, but the boot heel can overlap this region of ridges 40 in the forward and/or rearward direction.

FIG. 4 shows the bottom of the snowshoe 35, in the area of interest. The soft strike insert 22 is shown as having affixed to its bottom side a cleat 42, secured to the flexible insert piece 22 by rivets 44. The cleat 42 is formed of a harder plastic material, which can be a similar material to that of the molded snowshoe body (or of other hard material), and in a preferred embodiment is formed in a curved shape as shown. As explained above, when a heel strike occurs and the user's weight engages against the insert member 22 of the snowshoe, and weight is pressed down against the snowshoe engaging the terrain, the insert 22 can deflect downwardly, particularly if the terrain is uneven and the heel is over a low spot in the terrain, or if the snow is soft, and this heel cleat 42 will engage down into the terrain. It need not be directly under the heel but should be close.

FIG. 4 also shows metal rails 46 secured to the bottom side of the molded snowshoe body. These rails preferably are sinuous in shape, as indicated, and have teeth 48. Depending on the material, thickness and dimensions of the molded snowshoe body, these metal rails can add significant strength and stiffness to the snowshoe body, and they can provide a means of structural support for the pivot connection of the binding, as discussed above.

Also seen in FIG. 4 is another cleat 50, preferably of plastic and curving as shown, which is preferably integral with the molded snowshoe body or which can optionally be secured to the molded body by riveting. If connected to the molded body, this could be a metal cleat.

FIG. 5 shows an alternative embodiment of the invention, a molded snowshoe body 10 a which may be similar to the snowshoe body 10 shown in FIG. 1. In this form of the invention a sheet of material 52 is suspended across the open heel area of the snowshoe body, in lieu of the molded elastomeric insert shown in the first embodiment. The sheet insert 52 can itself be elastomeric material, and can be stretched across the opening and held in place by rivets on the molded body. Alternatively, this sheet can comprise a flexible but non-stretchable material such as a plastic coated fabric, or material similar to that typically used on Atlas snowshoes having a tubular peripheral frame supporting the decking material. The sheet 52 may be secured on the underside, as shown, or on the upper surface of the snowshoe body. Preferably, but not necessarily, a cleat of appropriate form can be secured to the underside of the soft heel strike insert sheet 52. If the insert sheet 52 is elastomeric material it can be of such materials as described above. Its performance in use can be as set forth above. As noted above, the snowshoe of the invention can be formed with a rear cleat secured to the soft heel strike insert, under or near the region in which the boot heel will rest, but the invention encompasses the molded snowshoe body with the soft heel strike insert (in both embodiments) whether or not such a cleat is included. Also, other appropriate materials than those described above, and other configurations for the insert member, can be employed in the snowshoe of the invention.

The above described preferred embodiments are intended to illustrate the principles of the invention, but not to limit its scope. Other embodiments and variations to these preferred embodiments will be apparent to those skilled in the art and may be made without departing from the spirit and scope of the invention as defined in the following claims. 

1. A snowshoe, comprising: a molded snowshoe body, defining a flotation surface and having an open area in a forward portion of the body, a boot binding connected to the snowshoe body so as to allow pitch pivoting of the snowshoe body relative to the boot binding so that a forward end of the boot binding can swing down into the open area during part of the user's gait, the molded snowshoe body having an open heel area in a heel strike region located below a heel of a user's boot when the boot in secured in the binding, and a soft heel strike insert secured to the molded snowshoe body and suspended across the open heel area and serving as a flotation surface along with the molded snowshoe body, the heel strike insert being of a flexible material, softer and more flexible than the snowshoe body, so as to deform vertically when weight of a user is engaged against the heel strike insert through the user's boot heel, whereby the soft heel strike insert reduces noise and increases comfort when a user's heel strikes the snowshoe during the user's gait.
 2. The snowshoe of claim 1, wherein the soft heel strike insert is formed of an elastomeric material.
 3. The snowshoe of claim 1, wherein the soft heel strike insert is secured to surrounding portions of the molded snowshoe body by riveting.
 4. The snowshoe of claim 1, further including a heel cleat for engaging terrain, secured to the underside of the soft heel strike insert.
 5. The snowshoe of claim 4, wherein the heel cleat is positioned to be directly under the user's boot.
 6. The snowshoe of claim 5, wherein the heel cleat is formed of hard plastic material, harder than the soft heel strike insert.
 7. The snowshoe of claim 1, wherein the soft heel strike insert comprises an elongated flexible body narrower than the open heel area of the molded snowshoe body and with a plurality of extending connection legs reaching the molded snowshoe body and connected by fasteners to the molded snowshoe body.
 8. The snowshoe of claim 7, wherein the soft heel strike insert is non-planar, with an upwardly relieved area for contact by the boot heel.
 9. The snowshoe of claim 1, wherein the soft heel strike insert comprises injection molded polyurethane.
 10. The snowshoe of claim 9, wherein the soft heel strike insert has a durometer range of about 70 A to 85 A.
 11. The snowshoe of claim 1, wherein the soft heel strike insert comprises a plastic coated fabric retained tightly across the open heel area. 